More than one in 10 British people don't realise that a woman can still get pregnant if she has sex standing up, according to a poll on Friday.
Nearly one in five - 19 per cent - are also unaware that a woman can get pregnant during her period, or if the man withdraws before ejaculation, according to the government-commissioned survey.
While 11 per cent believe that sex standing up is an effective contraceptive method, more than a third - 37 per cent - never talk about contraception with their partners at all.
"In spite of our love of talking about sex and relationships, the survey suggests it's our lack of knowledge that is causing confusion," commented sex and relationship expert Dr Pam Spurr.
Other findings from the poll of 2,000 people aged 16-50 include that 31 per cent never discuss sexual health with partners, while 17 per cent don't know that infections like herpes and genital warts are resistant to antibiotics.
More than a quarter - 27 per cent - admit to being too embarrassed to ask the questions they would really like, while 47 per cent never discuss their sex lives with their friends.
Even when they do talk about sex, 62 per cent turn the discussion into a joke, said the survey, commissioned by the Department of Health and the Department for Children, Schools and Families.
"I'm encouraged to see that we've overcome a long-held aversion to talking about sex," said Spurr.
"But we've still got some way to go before we swap jokes and banter for the open, honest and informed conversations about sexual health and relationships that most of us would like."
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